Check valve



FIG. 1 shows a front view of a check valve showing my new design;

FIG. 2 shows a rear view thereof;

FIG. 3 shows a right side view thereof;

FIG. 4 shows a left side view thereof;

FIG. 5 shows a top view thereof;

FIG. 6 shows a bottom view thereof;

FIG. 7 shows a top, front and right side perspective view thereof; and,

FIG. 8 shows a bottom, front and left side perspective view thereof.

CLAIM The ornamental design for a check valve, as shown and described.